Judge Gerard Winter ruled that Haiu's criminal record would remain clean so he could continue his battle with cancer, work overseas and support his wife and two children.
He said the Blues player was a role model to many, the attack was provoked by Cooper's actions and Haiu had accepted responsibility for his assault.
When the judge announced the sentence, Haiu's wife, brother and mother sighed with relief.
His mother, Yvonne, had tears in her eyes.
Haiu's lawyer, Richard Earwaker, earlier told the court there were several reasons behind the attack.
Haiu had lost $400,000 to $500,000 to Cooper after investing in unsuccessful property deals.
The rugby star has played 72 games for Auckland and 53 games for the Blues but has been on indefinite leave from rugby after being diagnosed with Ewings sarcoma, an unusual tumour on a rib.
The cancer diagnosis caused Haiu to lose a contract to play rugby in Japan, putting further financial pressure on his family.
Outside court, Haiu said with his wife by his side and friends and family behind him: "We're just happy it's all over. Now we can just put that behind us and get on with life."
He said he was talking to lawyers about taking legal action against Cooper.
"That's stage two. That's part two of our journey, we've got to sort that."
But his focus was on sorting out his health and career.
"I'm feeling good, I just want to get back into my training. I want to get back for next year."
He said he was looking at all cancer treatments, from chemotherapy to alternative remedies.
